In photographs of eggshell ultrastructure,
the size of mammillary cones and cracks in the outer
surface were decreased by dietary Mn supplementation.
The contents of GAG and uronic acids in eggshell membrane
were significantly increased by dietary Mn addition
(P < 0.05). This result was further confirmed by
increased mRNA expression and protein expression of
GlcAT-I when Mn was added to the diet. This study
suggests that dietary Mn supplementation can improve
eggshell quality by enhancing the GAG and uronic acid
synthesis in the eggshell glands, which can affect the
ultrastructure of eggshells.